The subject matter disclosed herein relates generally to heat recovery steam generator systems and, more specifically, to controlling temperature in a heat recovery steam generator (HRSG) system.
An HRSG may use gas turbine engine exhaust to heat a fluid flowing through heat exchangers in the HRSG. In some configurations, the fluid may be steam used for high-pressure, intermediate-pressure, and/or low-pressure sections of a steam turbine. Under certain conditions, such as when operating the gas turbine engine with a partial load or when operating at relatively high ambient temperatures, the fluid temperature in the heat exchangers may exceed designed temperature boundaries. Therefore, the HRSG may attempt to control fluid temperatures flowing through the heat exchangers. The fluid temperatures may be controlled to predetermined levels during operation of the gas turbine engine. Some HRSG systems may control the temperatures within the HRSG by attemperation. For example, such HRSG systems may spray a cool fluid into the heat exchangers to cool the fluid already in the heat exchangers. Such a method may cool the fluid temperature as desired; however, thermal efficiency of the HRSG system is lost due to switching from heating the fluid to cooling the fluid and then heating the fluid again. Consequently, such attemperation methods may result in reduced plant electrical output and efficiency. Accordingly, there is a need for a system and apparatus for controlling temperature in an HRSG system to improve the performance of the HRSG system.